AFN Engine: Starting Problems & Troubleshooting

Hello,
A friend of mine is having the following problem:
'The car's engine starts very poorly when it's warm. It takes several seconds each time. When it's cold, it starts immediately after a short pre-glow. At the recommendation of the workshop, the fuel filter was replaced, but this did not resolve the issue.'
His used car warranty expires in a month, so there's only this short window of time left to process any necessary repairs under it.
Who has an idea what might be causing this?

Hi.

If you haven't already explored: Use the search function for "Warmstart" and related terms .